1. Field of the Invention
This invention relates to novel formulations for the control of arachnids, especially Varroa destructor, an ectoparasite of the honey bee, Apis mellifera and to a novel strain of Beauveria bassiana. It also relates to methods for treating arachnids, especially Varroa destructor, using a formulation having a Beauveria bassiana and a carrier.
2. Description of the Related Art
Currently, there are several methods of controlling economically important pests such as Varroa mites. These methods fall into two broad categories-chemical and biological. Chemical methods are the most commonly used. However, chemical pesticides can pose risks to human health and cause environmental damage due to adverse effects on non-target insects and other animals. Chemical pesticides can kill pollinating insects, adversely affecting plant life or can upset insect population balances by killing predators or parasitic insects that naturally control the pest population.
Biological methods of controlling economically important pests have become increasingly attractive as a less ecologically destructive way of controlling pests such as arachnids and insects. Biological methods exploit an arachnid's and insect's natural enemies and include using parasitoids, predators and pathogens. Of the various ways to use an arachnid's and insect's natural enemies as biological control agents for that arachnid or insect, one of the most common is mass multiplying pathogens such as bacteria and fungi and applying them to an affected area as a biopesticide. Organisms which have been under investigation as potential biopesticides include viruses, nematodes, protozoa, bacteria, and fungi.
Varroa mites (Varroa destructor Anderson and Trueman) are an increasingly important pest of honeybees (Chandler et al., Biocontrol Science and Technology, volume 11, pages 429-448, 2001 Rinderer et al., Apidologie, Volume 32, pages 381-394 2001). Varroa destructor was found in continental Europe, northern Africa, and South America by 1975 (De Jong et al., Annual Review of Entomology, Volume 27, pages 229-252, 1982) and in the United States in 1987 (Chandler et al., supra). Infested colonies often die within two years. The mites do not cause massive acute mortality, but weaken larvae and adults by feeding on haemolymph, transmitting diseases, and inducing deformities (Chandler et al., 2001, supra; Martin, Journal of Applied Ecology, 2001). The impact of Varroa mites on both domesticated and feral colonies of A. mellifera in the United States has been profound; feral populations of A. mellifera, once common, have been almost completely eliminated by the mites (Rinderer et al, 2001, supra). The loss of wild colonies of A. mellifera has been felt most by farmers who depend on the bees for pollination of fruit and field crops.
Chemical control of Varroa mites has some drawbacks. Apart from issues of residues in wax and honey, mite populations resistant to the common chemical pesticides, fluvalinate and coumaphos, have been observed (Elzen et al, American Bee Journal, Volume 138, pages 674-676, 1998; Elzen and Westvelt, American Bee Journal, Volume 142, pages 291-292 2002; and Milani, Apidologie, Volume 30, pages 229-234, 1999). Biopesticides, and in particular, entomopathogenic fungi, represent alternatives to chemical insecticides in agricultural systems. Preparations of Bacillus thuringiensis are registered for the use against wax moth larvae (Galleria mellonella L.) in Europe. Several species of entomopathogenic fungi, including Beauveria bassiana (Balsamo) Vuillemin, have been found to infect Varroa mites in the laboratory (Kanga et al., Journal of Invertebrate Pathology, Volume 81, pages 175-184, 2002; Shaw et al, Biological Control, Volume 24, pages 266-276, 2002; Davidson et al., Journal of Applied Microbiology, Volume 94, pages 816-825, 2003; Meikle et al., Journal of Apicultural Research, Volume 45, Number 1, pages 39-41, 2006), and both Hirsutella thompsonii Fisher and Metarhizium anisopliae (Metschinkoff) have been shown to affect mite densities in honey bee colonies (Kanga et al, 2002, supra; Kanga et al., Journal of Economic Entomology, Volume 96, pages 1091-1099, 2003, Kanga et al., Biologist, Volume 52, pages 88-94, 2005).
Several criteria are used in evaluating a fungal biopesticide. The first criterion is the density of the mites in the bee colony, measured either by a) placing a rectangular piece of cardboard covered with glue (hereafter “sticky board”) and counting the mites that fall onto the board after a given amount of time; or b) by sampling large numbers of worker bees, treating the bees to remove the mites and then counting the bees and the mites to calculate a mite density per 100 bees. A second criterion is the rate of infection of the target pest, measured by collecting pests, in this case Varroa mites, placing them in environmental conditions under which the fungus will sporulate, such as on water agar in petri dishes, and counting the number of individuals that sporulate, compared to number that do not sporulate (the proportion of mite cadavers that sporulate is hereafter referred to as the “proportion infected mites”). The duration of the treatment can be measured as the length of time the infection rate of the pests exceeds background levels, and the spread of the treatment within an area, by movement of treated individuals, such as adult bees, can be measured by recording the infection rate in untreated areas. A third criterion is the impact of the biopesticide on the bee colony itself. Even if a product works well, beekeepers need to know the risk of harming the colony itself. Various forms of Varroa mite control are known, however there remains a need in the art for reliable control methods and traps for controlling Varroa mites. The present invention, as described below, is different from related art control methods, lures, and traps.